Skinning knife



May 6, 1952 J. J. PROHASKA SKINNING KNIFE 2 Si-IEETS-SHEET 1 Filed Aug. 23, 1950 INVENTOR. James I: probaska. 2'? m A rToN-EY May 6, 1952 J. J. PROHASKA 2,595,079

I SKINNING KNIFE Filed Aug. 23, 1950 v 2 smzms-snm 2 IN V EN TOR.

Jg n es Pro/la ska.

ATTORNEY Patented May 6, 1952 SKINNING KNIFE James J. Prohaska, La Grange, 111., assignor to Swift 8; Company, Chicago, 111., a corporation of Illinois Application August 23, 1950, Serial No. 181,015

Claims. 1

This invention relates to a skinning means and more particularly to a power-driven skinning knife.

The principal object of the present invention is to provide a power-operated skinning knife that will quickly and easily separate the hide from the remainder of the carcass without leaving an excess amount of flesh on the hide or damaging the hide during the removal operation. This is achieved through the use of a wedge-shaped cutting head which parts the skin and the fiesh in the out area to expose a small line of fibers between the skin and the flesh at the edge of the cut area, and allows the small cutting blade at the apex of the wedge to sever these fibers close to the skin. The sides of the cutting head form a guard to prevent the blade from reaching the skin, and the parting action achieved by the wedge-shaped head keeps the cutting blade centered along said line of fibers to be severed.

Additional objects and advantages include: to provide a power-driven skinning means having inherent safety features; to provide a skinning knife which automatically sharpens itself as it operates; to provide an improved cutting arrangement for severing the fell layer between the skin and the carcass of cattle and the like; and to provide an improved construction whereby a new cutting blade can be rapidly assembled in the power-driven cutting means to condition the device for use.

Other objects will appear from the specification below.

In the drawings:

Fig. 1 is a top plan View showing the handle, with the cutting means forming the subject of thi invention extending outwardly therefrom;

Fig. 2 is a top plan view partly broken away showing the cutting means, including the mounting means for the knife blade on the end of the power-driven means;

Fig. 3 is a view taken on line 3-3 of Fig. 2;

Fig. 4 is a perspective view showing the relationship between the guard teeth and the cutter blade teeth;

Fig. 5 is a view taken along line 5-5 of Fig. 8; Fig. 6 is a greatly enlarged elevational view of the teeth of the guard and cutting blades; and

Fig. 7 is a transverse section of the guard and cutting blades in cutting position on a carcass. The present application is a continuation-in part of my prior application Serial No. 676,225. Various means have previously been proposed as a substitute for the manual skinning of animals, and particularly cattle, but until the pres- 2 cut development, no completely successful means have been found useful for commercial cattleskin me e a o t is desir le @9213 power to this Cutting operation in order to speed it up and reduce the work which must be per.-

formed by hand. Such power means must be d e signed from the standpoint of safety to the operator and lightness for handling, coupled with the ability to perform a heavy-duty job. As above stated, many attempts have been made to sol ve the problem; however, all devices proposed to date have been rejected and, heretofore, even in the big packing plants, the skinning of cattle ha been practiced almost entirely as a manual art.

The present invention has been made to pro; vide a power means for this necessary cattle-skin,- ning task and it embodies the features of durabilr ity and lightness, together with an improved cut.- ting principle which has proven to behighly sat.- isfactory. The device of this invention takes the form of a pair of guard members betweenwhich a cutting blade reciprocates. The edges of the guard members and the cutting blade are each serrated and the individual teeth of the serrated edges cooperate so that as the blade moves between the guards, fibers falling between the teeth are sheared between a blade tooth and a guard tooth. The guard members are supported from the handle of the tool in such a manner as to snugly engage each side of the cutting blade whereby the blade is rubbed as it reciprocates and is thus continuously steeled during operation to dress the cutting edges.

Referring to the drawings, the preierred form of the device is shown therein, and inFig. l the guard elements are indicated as It and H, the cutting blade being denoted as I2. The guard member It, as best shown in Fig. 2, is fixedly mounted from the handle I? by means of a bolt [4 and a centering pin I5. The guard member H is supported from the handle l3 and guard. In in a floating manner and for this purpose is mounted upon a centering pin [6 at the handle and at its opposite end from a spring clip 20 integral with guard member in. The spring clip 20 is provided with a pin 2| upon which guard ll may be centered. A leaf spring is provided adjacent pin l6, and spring clip 20 and leaf spring 22 urge the floating guard l l toward the relatively fixed guard l6. When replacing a cutting blade, the guard member ll may be quickly removed from the knife by taking out the centering pin I6 and springing the guard member H from off of the centering pin 2|.

The reciprocally-driven cutting blade I! is mounted to move between the guard members if! and II and the blade I2 is removably carried at the outer end of a reciprocating drive element 3i slidably mounted in a bearing 29 fixed in the handle. The element 3| may be reciprocated by any suitable drive means and it has been found quite satisfactory to use a flexible cable 32 to transmit motion from a motor 35 to the handle 23 which contains a suitable gear and crank mechanism 36 to convert the rotary motion to a reciprocating the outer end of a reciprocating drive element 3! is bifurcated to provide a slot 33 to receive the inner end of the knife blade, one branch of the bifurcated end of the drive element being longer than the other. The longer branch carries a centering pin 34 which interfits with an aperture provided in the knife blade to fix'it to the drive element, and the pin and the slot cooperate with the end of the knife to hold it projected outwardly in a fixed position with respect to the drive element 3!.

The working edges of each of the guard elementslil and H and of the knife blade l2 are serrated as above explained to provide a set of shearing edges for cutting fibers falling between the teeth; such, for example, as in skinning cattle, the fibers of the fell layer holding the skin to the carcass. The teeth at the edges of the guard members l and l l are preferably arranged oppositely to each other while the teeth on the cutting blade are formed slantwise across the edge of the cutting blade for a purpose that will appear more fully below. Thus, the cutting blade teeth are preferably ground across the blade on an angle of between 30 to 45 as best seen in Fig. 5. The teeth on the guard members are designed to have a pitch approximately three to four times that of the pitch of the teeth on the cutting blade, and the cutting blade has a stroke about equal to the pitch of the teeth on the guard members.

The guard teeth are spaced wide enough apart to let fibers into the shearing edges, and for skinning cattle, the guard teeth are spaced about /4 apart. This spacing for cattle skinning permits the fell fibers to enter into the serration of the guards and the cutting blade while the skin and carcass surface can not ordinarily bend sharply enough to fall into the cutting means. The blade teeth are designed to be of a size to permit fibers to readily fall between them and, in general, the more teeth there are on the blade, the more extensive will be the shearing surface. For skinning cattle, blade teeth about 1% apart have been found best; a smaller distance tends to prevent the fell fibres falling into the serrated edge; yet, on the other hand, if the teeth are larger, the extent of the shearing surface is reduced. Thus, for skinning cattle, teeth on the blade are preferably ground on a re pitch with the guard teeth being spaced apart about 1 -6 to The cutting blade is designed to have a length such that when moved to the outer end of its stroke, approximately two teeth on the blade R? will project beyond the last pair of teeth A and B (Fig. on the guard elements. Thus, as the blade reciprocates, the two end teeth on the blades will alternately project beyond the last pair of the teeth on the guards and then be drawn inwardly between the guard members a distance approximately equal to two cutting blade teeth.

The blade is reciprocated quite rapidly and as the knife is pushed into the fell layer of the cattle carcass, the fibersof the fell fall into the space between the teeth on the cutting blade and are sheared upon being moved against the teeth on the guard members. As the knife drives in one direction or the other, fibers of the fell layer are sheared when the teeth on the cutting blade pass the teeth on the guard members. Due to the angular formation of the cutting blade teeth, it is seen that first one edge of a given tooth on the cutting blade will pass one edge of the oppositely disposed guard member teeth, and thereafter the other edge of the given blade tooth will pass into cutting relation with respect to the other member of the pair of guard teeth.

The disposition of the cutting blade teeth on an angle as clearly shown in Fig. 5 is important for the reason that whenever a particular fell fiber is caught between a blade tooth and a guard tooth, it is severed in only one point. This reduces the energy required to sever the fell layer to a minimum and eliminates the presence of fell fiber particles. It is obvious that if the teeth on the knife blade 12 were ground at an angle of across the face of the cutting edge, a fiber trapped between the teeth on the cutting blade and a pair of teeth on the guard members would be simultaneously cut at two points as the cutting blade moved along. This would require twice the cutting force and a discrete fell fiber particle equal in length to the width of the blade would be produced. This possibility is avoided by disposing the guard teeth with respect to the cutting blade so that first one edge of the cutting blade tooth passes a guard tooth and then the other edge of that cutting blade tooth passes the second guard member tooth. The same effect may be accomplished by disposing the teeth on the guard members slightly off center with respect to each other rather than directly opposite to each other.

In using this knife during the cattle-skinning operation, the nose of the knife, which is tapered to a rather thin point, is first inserted between the skin and the surface of the carcass to begin the separation of the fell layer. In general, the same system of separating the skin from the carcass is followed when using the power knife here described as is now practiced in manual skinning. While the carcass is held suspended from its hind legs, the knife is first inserted between the skin and the surface of the carcass at a point along a cut extending lengthwise of the belly of the carcass and a portion of the belly and each of the hind legs is cleared. Then the foreleg and neck section is operated upon. After the skin at the foreleg and neck area has been separated, the skin is freed from over the chest and shoulders of the carcass. The operator then goes back to the hind end and cuts the skin from the rump, leaving it still attached to the tail. The back area is then skinned with long sweeping cuts, always leaving the skin hanging from an area near the rump. After the back has been finally cleared, the skin is-pulled free from the carcass by stripping it from the tail. To expedite the skinning operation, the skin along the inside of the hind and forelegs is opened manually as conventional in cutting the pattern. Thereafter, however, the power knife is used to separate the skin from the legs and remainder of the carcass.

The pointed or tapered nose portion 7 of the knife serves during the skin opening operation and also fitsinto close quarters so that the power knife may be used around the sharp curves found at the shoulders and at other points around the carcass. It is important thatthe cutting blade assume 5. have a-stroke su-fliciently long to project several teeth beyondthelast pair of guard teeth as above explained, so that the fell layer in front of the nose section of the knife will be out. If this is not done, a heavier pushing force is required to drive the nose area of the knife, i. e. the pair of teeth A and'B' of guards Ill and l I, Fig. 5, through the fell layer.

In clearing the broad sections of the back, rump, and over the neck, long sweeping strokes may be made. As the operator moves the knife, first in one direction and then the other, the knife must-beturne'd-to present the shearing edge against the fell layer; It is conceivable that a shearing edge could be provided on each edge of the knife; however, this construction with its attendant complications has not been found necessary because of the arrangement made for connecting the drive means 32 to the handle l3. If, as-above stated, a flexible cable is preferably used to transmit rotary power from a motor to the motion converting means in the handle, the cable 32 may be connected to the handle through a suitable bearing joint such that the handle may rotate with respect to the fixed outer sheath of the cable. When such a connection is provided, the reaction of the handle l3 with respect to the inside drive member of the cable 32, will cause the handle to rotate if it is free. Thus if the operator momentarily relaxes his grip on the knife at either end of the long sweeping stroke, the knife will quickly spin so that the operator can grab it after it has turned through approximately" 180?" and the knife may then be moved in the opposite direction. In following this practies, the knife may be quickly reversed without effort on the part of the operator and only a single cutting edge need be provided.

The use of a thin blade snugly positioned between the two guards has a particular advantage in that the Weight of the reciprocating parts is minimized. Such structure makes possible the use of a lightweight, rapidly-moving drive mechanism.

Further, with the structure described above, the relatively thin cutting blade I2 is constrained to a movement between the two guard members Ill and l I. The guard members are preferably made of a harder material than the blade and, in anyevent, the blade is snugly positioned between theguard members such that a close rubbing contact results. This is occasioned by the resilient and "floating mounting of the guard member H so that it is biased toward the fixed guard member ID. The tension on the spring clip 20 and leaf spring 22 is such that a sufficient pressure is maintained so as to hold the knife blade against buckling without unduly binding the blade during its reciprocation. This structure serves the dual purpose of permitting the use of a relatively heavy driving force on a thin knife blade to accomplish the required shearing action during both the pulling and pushing stroke of the cutting blade while, at the same time, providing the means for sharpening the knife as the blade reciprocates.

During use of the knife, the blade is dulled to some extent and when the guard members are held snugly against the side faces of the cutting blade, the blade is rubbed so that it is continuously steeled during use. If the cutting blade becomes quite dull, it is necessary merely to hold the knife free of the carcass and let the blade reciprocate for a few moments to again condition the cutting edge for use. By providing such an inherent steeling action, it is possible by a suitable selection of blade and guard materials to provided a knife blade that may be used for from 4 to 8 hours at a time Without requiring honing or grinding.

Figs. 6 and 7 illustrate a form of the invention utilizing a wedge-shaped knife formed by the tapered guard blades 45 and 46, between which is positioned the thin cutting blade 41. In the embodiment illustrated, the lower edges of the guard blade teeth: are milled on as illustrated art-4B to form the wedge-shapedteeth. Thelower ends of the teethare' rounded off as illustrated at-49 to form a smooth nose. at the end of the guard blade teeth. The. remaining structure of the:knifeissubstantially identical with that previously described in conjunction with Figs; '1' through. 5.

Fig.7 illustrates the action of the knifein: separating the'skinr 5| from the remainder of the carcase 52. Thewedge-shaped nose. of the knife formed by flats 48 and the roundednoses Mlholds the skin and'the carcass apart in the form. of a V, exposing the plurality of small fibers 53 at the point of the V holding the skin to the meat. The cutting blade 41, the teeth of which project slightly beyond the rounded ends of the two guard blades 45 and 46, catches'the fibers 53 and by'its movement pulls them against the guard blade teeth to. continuously snip the fibers. A slight. pressure on the knife will push the nose of the knife into the cut area, wedging the skin 51 away from the remainder 'ofthe carcass 52 to further expose additional fibers 53 to be cut.

Preferably, the teeth of the cutting blade 41 extend beyond the teeth of the guard blades 45 and 46 approximately one-third the depth of the cutting blade teeth. trated in Figs. 6 and 'l, the spacing of the cutting blad teeth is T e" and their depth is approximately 1 6". Thus, if a plane were placed across the. ends of the rounded noses 49 of the guard blades 45 and 46, the cutting blade 41 wouldlproject preferably about .020" beyond that plane.

In order not to complicate the illustration of Fig. '7, no eifort has been made to show how the relatively wide spacing of the guard blade teeth permits the skin and flesh to work into the openings between those teeth in a position where they are close to the teeth of the cutting blade 41. However, a study ofFig. 6 will illustrate the fact thatin addition to the guard blade teeth being wedge-shaped so as to permit the apex of the wedge to be inserted close to the skin and flesh, the teeth are widely spaced with relation to the teeth of the cutting blade 41 with the root 54 of the guard teeth well above the remaining portions of the tooth lying in a corresponding 1ongitudinal plane.

The use of a small number of guard blade teeth with respect to the number of cutting blade teeth thus reduces the obstruction to the sides of the cutting blade teeth and better exposes said cutting blade teeth to reach in close to the skin and flesh, while, at the same time, not materially reducing the speed of cutting of the knife. As each of the small teeth on the cutting blade passes a large tooth on the guard blades, there is a snippin of the fibers caught therebetween, and a large movement of the cutting blade is not required to produce one severing action between the cutting blade and a guard blade.

The foregoing description is for the purpose of complying with Section 4888 of the Revised Statutes and should not be construed as impos- In the embodiment illus 7 ing any unnecessary limitations on the appended claims. It is conceivable that modifications may occur, to those skilled in the art, which modifications are within the scope of the invention a defined by the following claims.

I claim: l.- A device for skinning cattle and the like including handle means, a pair of elongated guard blades, each having an elongated, serrated edge, a reciprocally-driven, elongated cutting blade disposed between said guard blades and having-an elongated, serrated edge adjacent the serrated edges of said guard blades, one end of one of said guard blades being attached to said handle means, the corresponding end of the otherjof said guard blades being pivotally connected to said handle means,a clip interconnecting the other ends of said guard blades and urging saidother ends of said guard blades toward each other, and spring means urging said one end of the other of said guard blades toward the corresponding end of the one guard blade.

2. A device for skinning cattle and the like including handle means, a pair of elongated guard blades, each having an elongated, serrated edge forming relatively pointed teeth, the points of said teeth of said two guard blades being positioned in a common plane, a reciprocally-driven, elongated cutting blade disposed between said guard blades and having an elongated, serrated edge forming teeth said serrated edge or" said cutting blade being adjacent the serrated edges of said guard blades, said serrated edge of said out-- ting'blade being positioned out of said plane a distance such that said serrated edge or" the cutting blade projects beyond the said plane a distance less than the depth of said teeth, one end of one of said guard blades being attached to said handle means, the corresponding end of the other of said guard blades being pivotally connected to said handle means, a clip interconnecting the other ends of said guard blades and urging said other ends of said guards blades toward each other, and spring means urging said one end of the other of said guard blades toward the corresponding end of the one guard blade.

3. A device for skinning cattle and the lik including handle means, a pair of elongated guard blades, each having an elongated, serrated edge forming relatively pointed teeth, the points of tween said guard blades, said cutting blade hav'-: ing teeth in the edge thereof adjacent the teethof said guard blades, said edge of said cutting,

plane a distance such that said serrated edge of the cutting blade projects beyond the planea distance less than the depth of said teeth.

4. A device for skinning cattle and the like including handle means, a pair of elongated guard blades, each having an elongated edge with teeth formed thereon, said blades beingattached to 'said handle means, the ends of said teeth of said blades being positioned in a common plane, the adjacent faces of said blades along said tooth edge being relatively flat, the other faces oi said blades being rounded ofi adjacent- 5. A device for skinning cattle and the like including handle means, a pair of elongated guard blades, each having an elongated edge with teeth formed thereon, said blades being attached to said handle means, the ends of said teeth of said blades being positioned in a common plane, the adjacent faces of said blades along said tooth edgebeing relatively fiat, the

other faces of said blades being rounded off adjacent the ends of said teeth, and a reciprocallydriven, thin, elongated cutting blade disposed beblade projecting beyond said plane a distance substantially equal to one-third the depth of the teeth on said cutting blade.

JAMES J. PROHASKA.

REFERENCES CITED The following references are of record in the file of this patent:

"UNITED STATES PATENTS Number Name Date 636,724 I-Iacherelle Nov. 7, 1899" 1,326,166 Backus Dec. 20, 1919" 1,832,993 Masek 'Nov. 24, 1931 1,838,186 Moodhe Dec. 29 1931 2,488,436 Santoro Nov. 15, 1949' FOREIGN PATENTS Number Country Date 340,662 Italy Mar. 25, 1936 

